run naphthas are routinely analyzed using this technique. A typical analysis is shown in Table I1 and is compared to the results of the conventional procedure. A comparison is also made with the results of the conventional method after correction for errors introduced h y the depentanization. These errors include approximately 1.5% light ends that are habitually left in the depentanized fraction and approximately 3.5% CS components that are often cut out of it. The corrections are based solely on the gas chromatographic analyses of the overhead and bottoms of the depentanizations. T h e analytical results ot the new technique are in good agreement with those of the corrected conventional method. but differ significant11 from the uncorrected one.
The repeatability of the new method was determined to be 0 . 6 7 ~a t the 95% confidence level and compares favorably to the 2.470 obtained for the conventional procedure. The analytical technique presented here is therefore more accurate and precise than the conventional mass spectrometric method of analysis. Furthermore. the lengthy depentanization procedure is no longer required and high pressure process streams may be analyzed at their sampling pressures. T o date. the technique has been applied solely to lowolefinic stocks. It should also be applicable to olefinic streams. Received for review August 21, 1973. Accepted Sovember 5, 1973.
Semimicro Procedure for the Determination of Hydrocarbon Types in Shale-Oil Distillates Larry P. Jackson,l Charles S. Allbright,* and Howa,rd B. Jensen U.S. Department of the Interior. Bureau of Mines. Laramie E n e ~ g yResearch Center. Laramie. Wyo. 82070
T h e characterization and analysis of crude shale oil:< and their various distillate fractions have been objectives of the work carried out a t the Laramie Energy Research Center. Analysis of the crudes usually involves the quantitative determination of five general compound types: t a r acids, tar bases, saturates, olefins. and aromatics. For the purposes of this paper. t a r acids and t a r bases are referred to as polars; saturates, olefins, and aromatics are hydrocarbons. The limited quantities of sample frequently encountered in research and development make it very difficult to apply, with accuracy. standard methods of analysis such as acid absorption ( I ) , bromine number (2), and silica gel chromatography ( 3 ) because of the subjective judgments that must be made in each test. This paper describes a n analytical procedure based on a new application of the reaction of olefins with diborane in the quantitative determination of saturates, olefins. and aromatics in shale oil. Two major sources of difficulty in the analysis of shaleoil distillates are the high concentrations of nitrogen compounds and olefins. In the procedure reported here, the first of these problems is circumvented by the removal of the nitrogen compounds and the other polars from the hydrocarbons by column chromatography on Florisil ( 4 ) . For the purposes of this study. no further characterization was done on the polars. Because of the high concentration of olefins in the hydrocarbon fraction, accurate analysis by
* Present address, Department of Biochemistry. University of Wyoming, L a r a m i e . R y o . 82070. Correspondence should be addressed tn this author at the Laramie Energy Research Center. (1) "ASTM Book of Standards, 1971," Part 17, Method D 1019-68, "Olefinic and Aromatic Hydrocarbons in Petroleum Distiliates." pp 34251. ( 2 ) Ref. 1, Method D 1159-66, "Bromine Number of Petroieum Distillates and Commercial Aliphatic Olefins by Electrometric Titration." pp 378-89. ( 3 ) Ref. 1. Method D 1319-70, "Hydrocarbon Types in Liquid Petroieum Products by Fluorescent Indicator Adsorption," pp 474-79. ( 4 ) G. U. Dinneen, J. R Smith, R A. Van Meter, C. S Allbright. and W. R. Anthoney. Anal. Chem.. 27. 185 (1955).
604
A N A L Y T I C A L C H E M I S T R Y . VOL. 46, NO. 4 , A P R I L 1974
fractionation on silica gel is difficult, especially on small samples (5). In the present analytical scheme. the wellknown reaction between olefins and diborane is used as the key step in the selective, destructive removal of olefins from the hydrocarbon fraction (6). The reaction is carried out on a sample consisting of a 1:l mixture of the hydrocarbons from a shale-oil distillate fraction and a suitable internal standard made u p of n-alkanes and nalkylcyclohexanes whose boiling points are a t least 25 "C removed from that of the hydrocarbon fraction. Gas chromatography (GC) is used as the d a t a readout to determine the ratios of sample to internal standard before and after treatment to remove the olefins. The difference in the two ratios is a measure of the olefin content. The percentage of saturates is determined on another portion of the s a m e sample solution by selective removal of both the olefins and aromatics with a modification of the HzSO4P205 acid absorption procedure ( I ) . T h e resulting raffinate is a:ialyzed by the same gas chromatographic technique. T h r value obtained for saturates is combined with the olefin \,due and the result is used to calculate the percentage of aromatics in the sample. The procedure which we propose uses modern GC techniques for wiiich the precision of any given quantitative measurement is about *l%. This degree of precision is seldom attainable in classical methods of analysis where a subjective judgment often has to be made in tests that give no clearly defined end points or separations and where cornpetink; chemical reactions give erroneous results. SpecificalilJ, acid absorption end points are frequently diffuse when samples are rich in aromatics and olefins; bromine number values are affected by nitrogen compounds and alpha olefins, both of which occur in high concentrations in
